Only a small section of the building was damaged in the fire, allegedly started by striking municipal workers, Captain Stephen Marais said.
“The cause of the fire is under investigation and our forensic teams are on the scene.”
Earlier on Wednesday, police were keeping an eye on striking municipal workers in the area.
“The workers are waiting for management to finish negotiating in the Buffalo City municipal offices,” said Marais.
Police fired stun grenades and rubber bullets to disperse protesters on Tuesday.
Mayor Zukiswa Ncitha said at the time that the employees, mostly general workers, wanted 14th cheque payments from the municipality. She said she was unable to accede to their demands.
She said the Buffalo City municipality would have to obtain a circular from the SA Local Government Association with a bargaining agreement attached to implement the workers’ demands.
“That is how the law goes. We would be breaking the law if we give in to their demands. We have explained this issue, but unfortunately, the workers would not accept it and are still on strike,” she said.
The unions involved are the Independent Municipal and Allied Trade Union and the SA Municipal Workers’ Union.